The present application relates generally to bone fracture repair, and more specifically, to osteosynthetic implants for fracture repair and methods of their use and manufacture.
In 1959, a group of Swiss Orthopedic and General Surgeons formed the Arbeitsgemeinschaft fur Osteosynthesefragen (AO), also known as the Association for the Study of Internal Fixation (ASIF). The AO/ASIF is now a multi-national group of doctors and scientists with the expressed purpose of studying bone healing and continuous development of fracture fixation techniques for patient care. In the United States, as well as most other countries, AO/ASIF guidance regarding skeletal fixation has become the standard of care for traumatic fracture as well as therapeutic osteotomy fixation techniques. It is under these AO/ASIF guidelines that the surgeon plans and carries out procedures to achieve the desired end result of bone healing and skeletal function.
Problems can arise when the bone fracture or fusion site is not sufficiently stabilized during the healing timeframe. Depending on the nature of the fracture, screws and plates may be used alone, or in combination. One objective of osteosynthetic implants is the anatomic reduction of the fracture. Another objective would be to minimize or eliminate interfragmentary motion. Still another objective involves increasing or maximizing blood supply to the fracture site by reducing or minimizing additional vascular damage. Sustained compressive therapy can also be osteoinductive, due to its piezoelectric effects on osteoblasts themselves. Excessive interfragmentary motion results in the formation of fibrous, unmineralized scar tissue (resulting in a non-union or pseudo-arthrosis) versus the regeneration of bone. The unmineralized scar tissue is not load supporting and skeletal function is lost. A sufficient blood supply must be maintained to support skeletal metabolism, bone regeneration, and remodeling of the fracture site. The current standard of care includes osteosynthetic devices that are made of either stainless steel or titanium.
The use of stainless steel or titanium in osteosynthetic devices has a long history and reasonable record of success. Over time, however, the stainless steel and titanium fixation constructs (both screws and plates) do not maintain compression across the fracture fragments. The reduction of compression of certain standard material constructs has been observed to be thirty-two percent (32%) over a two week period. As the necrotic surfaces of the fracture are resorbed, a non-load bearing gap develops between the fragments, thereby decreasing compression and increasing the risk of interfragmentary motion and scar tissue formation. Loss of compression is contrary to the objectives of fracture fixation in general, and osteosynthetic implants in particular. Improvements are desired to help maintain compressive load across the fracture site over a longer period of healing.